Sheet registering apparatus

ABSTRACT

Apparatus to register and align a cut sheet of support material prior to the support material being forwarded to the xerographic transfer station. Register stop rolls are positioned prior to the transfer station and are programmed by means of a cam and gear arrangement to arrest the leading edge of a sheet of material as it is forwarded from a sheet feed tray. The sheet is registered in the stop rolls and is held in friction-driving contact with stop rolls by means of a pair of idler rolls cammed into operative relation therewith. The stop rolls are rotated rapidly to accelerate the sheet of material to the desired constant velocity at which time a second pair of cooperating feed rolls adapted to forward the sheet to the transfer station are cammed into engagement with the moving sheet. For a brief period of time the sheet is being positively driven towards the transfer station by the two drive means. The register stop rolls are programmed to release the sheet prior to completing one revolution and the remaining forwarding function completed by the second set of drive rolls.

llite @ttes tent [72] Inventors Merton l-l. SpearJr.

lenfield; John R. Caldwell, Rochester, both of, N.Y. [2!] Appl. No. 833,929 [22] Filed July 3, 1969 [45] Patented Aug. 24, 11971 (73] Assignee Xerox Corporation Monroe, NY.

[54] SHEET REGHSTERHNG APPARATUS 3 Claims, 7 Drawing Figs.

[52] {1.8.0 271/53 [51] lint. 1865i]: 9M0 [50] Field of Search 271/50, 53, 60, 51,9

[56] References Cited UNITED STATES PATENTS 1,241,897 lO/l9l7 Ananson 27l/9X 3,28Ll44 10/1966 Turneretaln... 27l/60X 3,517,923 6/l970 Hoffman et al. 271/53 Primary Examiner-Joseph Wegbreit Assistant Examiner-Bruce Hi Stoner, Jr.

Artorneys-Norman E. Schrader, James J. Ralabate and Michael J. Colitz, .lr.

ABSTRACT: Apparatus to register and align a cut sheet of support material prior to the support material being forwarded to the xerographic transfer station Register stop rolls are positioned prior to the transfer station and are programmed by means of a cam and gear arrangement to arrest the leading edge of a sheet of material as it is forwarded from a sheet feed tray. The sheet is registered in the stop rolls and is held in friction-driving contact with stop rolls by means of a pair of idler rolls cammed into operative relation therewith. The stop rolls are rotated rapidly to accelerate the sheet of material to the desired constant velocity at which time a second pair of cooperating feed rolls adapted to forward the sheet to the transfer station are cammed into engagement with the moving sheet. For a brief period of time the sheet is being positively driven towards the transfer station by the two drive means. The register stop rolls are programmed to release the sheet prior to completing one revolution and the remaining forwarding function completed by the second set of drive rolls.

PATENTED M624 1971 SHEET 1 BF 5 INVIZN'I'ORS MERTON R. SPEAR JR.

BY JO R. CALDWEL L I {I J A T TORNEV PATENTED M824 um SHEET 2 UF 5 PATENTED m4 m1 3601.392

I SHEET 3 [1F 5 SHEET REGISTERING APPARATUS This invention relates to apparatus'for registering and forwarding sheets to a work station and, in particular, to apparatus for registering and aligning the leading edge of a sheet and advancing said sheet to a subsequent work station.

Although this registration device is well adapted for use in many types of automatic apparatus calling for the processing of cut sheets of material, it is shown herein specifically embodied in an automatic xerographic reproducing apparatus. In the art of xerography, as disclosed by Carlson in U.S. Pat. No. 2,287,691, a 'plate comprising a conductive backing upon which is placed a photoconductive insulating material is charged uniformly and the charged photoconductive surface exposed to a light image of an original document to be reproduced. The photoconductive coating is caused to become conductive under the influence of the light image so as to selectively dissipate the electrostatic charge found thereon thus producing what is known as a latent electrostatic image. This latent image is developed by means of a variety of pigmented resins which have been specifically developed for this purpose. The pigmented resin material, or toner, is electrostatically attracted to the latent image on the photoconductive surface in proportion to the charge found thereon. That is, areas of small charge concentration become areas of lower toner density .while areas of greater charge concentration become proportionally more dense. The developed image is generally transferred to a final support material, as for example paper, and the image fixed thereto to form a permanent record of the original document.

Although it is possible to process support material in web configuration through an automatic xerographic machine, the more general practice is to transfer the developed image directly from the photoconductive surface to a cut sheet of final support material thereby eliminating the time and apparatus needed to process the web into cut sheets of conventional size. As can be seen, the size of the xerographic reproducing apparatus is also reduced by processing cut sheets of support material. A further advantage of processing cut sheets is the relative ease afforded the operator when a change in size and weight of material is needed.

In an automatic xerographic reproducing apparatus each individual sheet of support material must be accurately registered and aligned before it is forwarded to the xerographic processing stations coordinated that the intelligence data is properly placed thereon. That is to say, the movement of a sheet is coordinated with the timing and positioning of the xerographic image to effect registered transfer of the image to the support material. Many registration devices are known in the art, however, all have certain disadvantages which make them undesirable for use in automatic apparatus.

Slippage has heretofore been the prime problem associated with high-speed sheet-feeding devices. The registering of a sheet in process, prior to the sheet being forwarded to a work station or the like, usually requires that the movement of the sheet be retarded or stopped during registration. During this period the sheet-driving device is generally maintained at the predetermined operating or process speed and is either disengaged from driving contact with the sheet or permitted to slip during registration. To bring the sheet material back to the desired process speed, the drive means is simply brought once again into friction-driving contact with the sheet. Because the driving force is delivered through a friction contact driving mechanism, a certain amount of mechanical slippage occurs at the interface before the sheet can be brought up to the desired speed. Many machines are designed to allow for this slippage resulting in a decrease in useable machine time. When not allowed for or when excessive, slippage tends to negate the accuracy'attained during registration by causing late sheet delivery or delivery of skewed sheets.

It is therefore an object of this invention to improve apparatus for registering and forwarding sheet material.

A further object of this invention is to improve sheet-feeding mechanism for seriatim feeding of sheets in timed relation with the formation of a powder image on a xerographic drum of an automatic xerographic reproducing apparatus.

Another object of this invention is to improve apparatus for registering and aligning the leading edge of a cut sheet of material prior to the delivery of said sheet to the transfer station of an automatic xerographic reproducing apparatus.

Yet another object of this invention is to eliminate slippage in a sheet-registering and aligning device.

A still further object of this invention is to increase the useable machine time in an automatic reproducing apparatus by decreasing the amount of time required to register and align cut sheets of support material being processed therethrough.

These and other objects of the present invention are attained by register stop rolls which are arranged to intercept the movement of a sheet of support material being forwarded to a xerographic transfer station, means to program the motion of said stop rolls whereby the interrupted sheet is positively accelerated to a predetermined constant velocity, and then released by said rolls and further drive means programmed to engage the sheet moving at the predetermined velocity to complete the forwarding of said sheet into said transfer station, said drive means engaging the sheet prior to its release from said stop rolls.

For a better understanding of the invention as well as other objects and further features thereof, reference is had to the following detailed description of the invention to be read in conjunction with the accompanying drawings, wherein:

FIG. 1 illustrates schematically a preferred embodiment of a xerographic apparatus constructed in accordance with the invention;

FIG. 2 is a front view of the sheet registering device of the present invention;

FIG. 3 is a right-hand side elevation of the apparatus of the instant invention shown in FIG. 2;

FIG. 4 is a sectional end view taken along lines 44 in FIG. 2 and showing the sheet guides and register stop rolls of the instant invention;

FIG. 5 is a partial end view shown in partial section taken along lines 5-5 in FIG. 2 and showing the registering stop roll program cam and associated motion-translating mechanism of the sheet-registering device shown in FIG. 2;

FIG. 6 is a partial left-hand side elevation of the sheet registering device shown in FIG. 2;

FIG. 7 is a timing diagram of the operation of the sheet-registering device.

The general apparatus of the instant invention is shown herein embodied in an automatic xerographic apparatus. However, it should be clear that the apparatus of the present invention is equally adapted for use in any type apparatus requiring the registration and alignment of individual sheets of material, as for example, cut sheets of paper. As shown schematically in FIG. 1, the automatic xerographic reproducing apparatus comprises a xerographic plate 10 including a photoconductive layer or light-receiving surface which is placed on a conductive backing and formed in the shape of a drum. The drum is mounted on a shaft 11 and journaled in the machine frame (not shown) to rotate in the direction indicated by the arrow thus causing the drum surface to sequentially pass a plurality of xerographic processing stations.

For the purpose of the present disclosure, the several xerographic processing stations in the path of movement of the drum surface may be described functionally as follows:

a charging station A, at which a uniform electrostatic charge is deposited on thephotoconductive layer of the xerographic drum;

an exposure station B, at which a light or radiation pattern of an original document to be reproduced is projected onto the drum surface thereby dissipating the charge found thereon in the areas exposed to form a latent electrostatic image of the original document;

a developing station C, at which a xerographic developing material including toner particles having electrostatic charge opposite to that found on the electrostatic latent image are cascaded over the upwardly moving drum surface causing toner particles to adhere to the electrostatic image to form a xerographic powder image in the configuration of the original to be reproduced;

a transfer station D, at which the xerographic powder image is electrostatically transferred from the drum surface to a sheet of final support material; and,

a drum cleaning and discharge station E, at which the drum surface is wiped by a doctor blade to remove residual toner particles which may remain thereon after the transfer opera tion and at which the drum surface is exposed to a source of illumination to effect substantially complete discharge of any residual electrostatic charge remaining thereon.

The charging station is preferably located in the position indicated by reference character A in FIG. 1. The charging arrangement includes a corona-charging device 13 which includes a corona discharge area of one or more corona discharge electrodes that extend transversely across the drum surface and are energized from a high potential source. The corona discharge electrode is substantially enclosed within a shielding member and is adapted to generate a charge within confined area.

Next subsequent thereto in the path of motion of the xerographic drum is an exposure station B. An optical scanning or projection system is provided to project a flowing light image onto the moving drum surface from an original document supported on flat stationary copy board 14. Basically the optical scanning or projection assembly comprises the stationary copy board which consists of a transparent platen positioned on the exterior of the cabinet and which is adapted to support an original document to be reproduced. means to illuminate uniformly the original document and which is arranged in light-projecting relationship to the moving .photoconductive surface of the drum. Uniform lighting is provided by a single aperture lamp LMP-l attached to a carriage, and the carriage mounted for movement parallel to the plan of the copy board.

A folded optical system including an object mirror 16, a movable lens 17. and an image mirror 18 is used to direct the light image of the original onto the drum surface in this preferred embodiment of this invention. The lens element is positioned beneath the copy board and is arranged for movement in a path parallel to the plan of the copy board and is adapted to move in timed relation to the movement of the light source whereby the subject image of the original document supported by the copy board is scanned in timed relation to the movement of the light-receiving surface of the xerographic drum to project a light image corresponding to the original document onto the surface ofsaid drum.

Positioned adjacent to the exposure station is fadeout panel 19 which is arranged to exposure the drum surface in the areas between latent electrostatic images found thereon so that these nonimaged areas are not developed as the drum moves through the subsequent developing station. The fadeout panel reduces the charge on the drum surface below the level required for development.

Next adjacent to the exposure station is a developing station C in which is positioned a developer apparatus 20 which includes a casing or housing 28 having a lower sump portion capable of accumulating a quantity of developer material therein. A bucket-type conveyor 27 having a suitable driving means is used to carry the developer material from the sump portion of the developer housing to the upper part of said housing where it is cascaded over the upwardly moving drum surface by means of a hopper chute 29. As the developer material is cascaded over the drum, toner particles are pulled away from the carrier component of the developer material and deposited on the drum surface in relation to the charge pattern found thereon to form a xerographic powder image. The partially denuded carrier material passes from the drum surface back into the developer housing sump. Fresh toner powder is supplied to the developer material in proportion to the amount of toner deposited on the drum surface by means of a dispensing apparatus, generally designated 21.

Positioned next and adjacent to the developing station is the image transfer station D which includes sheet feeding and registering device adapted to feed individual sheets of paper successively to the xerographic drum in coordination with the presentation of the developed image on the drum surface at this particular station. The sheet-registering device, generally designated 22, will be described in greater detail below. The transfer of the xerographic powder image from the drum surface to the final support material is effected by means of a corona-generating device 24 that is located at or immediately after the point of contact between the sheet transfer material and the rotating drum surface. The corona transfer device is substantially similar to the corona discharge device employed at charging station A. In operation, the electrostatic field created by the corona discharge device is effective to tack the transfer material electrostatically to the drum surface whereby the transfer material moves synchronously with the drum while in contact therewith. Simultaneously with the tacking action, the electrostatic field is effective to attract the toner particles comprising the xerographic powder image from the drum surface and force the particles to adhere electrostatically to the surface of the transfer material.

Subsequent to the transfer station is positioned a plurality of mechanical fingers 25 positioned to come into contact with the lower leading edge of the support material and being adapted to strip the leading edge of the material from the drum surface The stripper fingers are shaped to direct the sheet material towards stationary vacuum transport 26. The sheet is held in contact with the bottom surface 0 the vacuum transport by means of vacuum ports positioned therein. The support material, a portion of which is electrostatically adhered to the drum surface is moved along the vacuum transport towards fuser assembly 30 as the drum rotates in the direction indicated.

Under the influence of the rotating drum, the support material is moved along stationary vacuum transport 26 into the nip between upper fuser roll 31 and lower fuser roll 32. The rolls of fuser 30 coact to deliver pressure-driving force to a sheet of support material therebetween. A radiant source of energy 33 extending transverse to the lower roll, transfer heat energy to the roll surface. The energy is then brought into thermal contact with the image bearing support material as the lower roll is rotated in the counterclockwise direction. Image fixing is accomplished by a combination of pressure and heat energy transferred to the powder image as the support material moves through the fuser assembly. The fixed copy is transported through a circular paper path to a secondary feed tray 35 or the sheets are discharged from the apparatus into catch tray 36 at a suitable point for collection. Movable guide and drive roll assembly 37 is pivotally mounted in the xerographic apparatus and is programmed by the machine logic system to be positioned in accordance with the mode of opera tion selected. At the same time the secondary feed tray is conditioncd to accept simplexed sheets from guide assembly 37. For further details concerning the specific construction and operation of the movable guide and feed roll assembly reference is had to copending application Ser. No. 838,953 filed in the name of Merton J. Spear, Jr.

The final processing station in the xerographic machine is the drum-cleaning station E having positioned therein preclean device 39; a drum-cleaning device, generally referred to as 40, adapted to remove residual toner from the drum surface by means of doctor blade 41; and an erase panel 43 adapted to expose the xerographic drum with sufficient energy to cause dissipation of any residual charge remaining on the drum surface. 1

Removal of residual powder from the drum surface is accomplished by means of doctor blade 41 mounted transverse to the drum and arranged to be maintained in intimate contact across the photoconductive surface thereon. Residual toner removed by the blade falls into atrough area behind the blade and the residual toner is carried away from the drum area by means of auger 42. The residual toner returns to the developer housing 28 by means of a toner conveyor system (not shown) where it is sued to recharge the developer system.

A single drive means is provided to drive the drum, movable lens, sheet feed mechanism, and fuser rolls at predetermined speeds in relation to each other and to also effect operation of the developer conveyor system and other operating systems.

It ,is believed that the foregoingde'scription is sufficient for the purposes of this application to shown the general opera tion of a xerographic reproducing apparatus using a sheet-retion.

Referring now to the subject matter of the instant invention, sheet-registering device 22 is supported in the machine frame (not shown) and is arranged to accept single sheets of support material from either of two supply trays, 34 or 35. When guide and roll assembly 37 is moved to the dotted position as shown in FIG. 1, a circular paper path is provided through the xerographic apparatus by which a sheet ofsupport material is capable of being fed twice through transfer station D. The individual sheets are programmed by the machinelogic system to be fed from the primary'tray 34 through the transfer station where one side of the sheet is xerographically imaged and the sheet then transported into secondary trays 35. On demand from the machine control system, guide assembly 37 is repositioned and the simplex sheet fed from secondary tray 35 into the transfer station. A second image is placed on the other side of the sheet and the duplex copy discharged from the apparatus into catch tray 36. Prior to entering the transfer station, the. individual sheets of support material are first I separated and forwarded :seriatim by the sheet. feed mechanism associated with the individual trays into sheet registering device 22 wherein the leading edge of the individual sheets are registered and aligned. After registration, the movement, of the sheets are accurately programmed so that sheets are forwarded into the transfer station in timed relation with an image found on the xerographic drum surface. As shown in FIG. 4, a series of guide members are positioned in sheet-registering device 22 to accept individual inlet guides are arranged in a funnel-type configuration such that the forwardly moving sheets are directed into a constrained or necked down area between the guides as the sheet approaches the register stop rolls. Lower inlet guide 87 has an extended portion thereon directed downwardly and which extends beyond the neck towards the transfer station. An aperture 58 is provided in lower guide 87 through which register pressure roll 69 is able to coact with register stop roll 60. The portion of the sheet-registering device wherein the register stop roll coact with pressure rolls 69 is herein referred to as the registration station.

Register stop guide 88 is positioned in relation to the extended portion of guide 87 to direct a sheet of support material forwarded through the lower inlet guides through the register stop roll station into the subsequent xerographic transfer station. A second aperture 59 is machined in register' stop guide 88 through which the stop rolls 60 is able to operatively communicate with both a sheet passing through the registration stop station and with coacting register pinch rolls 69.

Upper inlet guides 92 and 91 are likewise positioned in sheet-registering device 22 to accept therebetween sheets separated and forwarded by sheet feed mechanism 51 associated with the secondary feed tray 35 (FIG. 1). I-Iere again the inlet guides are arranged substantially in a funnellike configuration and function to direct sheets movedtherebetween gistration device constructed in accordance with this inveninto cooperating advancing rolls 96 and 97 comprising the sheet-registering device secondary sheet feed mechanism. This secondary sheet feed mechanism is provided within sheet-registering device 22 in order that the individual sheets of material fed from the more remote upper feed tray are positively driven into registering contact with register stop rolls 60.

The sheets are forwarded by means of the secondary sheet the intermediate guides is made movable to allow the machine or torsion spring 99 (FIG. 6) is affixed to end plate 56 by means of rivet 100 on the opposite end of the spring is operatively connected to extended stop arms 101 (FIG. 2) of guide 95 was to bias the guide in the closed or operative position against the end plates as shown in FIG. 4. To gain access to the intermediate paper pass the operator simply pulls down against the biasing pressure causing the guide to swing downwardly about pivot prongs 98 thus exposingthe intermediate paper path.

Driving power to the sheet-registering device is provided from the xerographic reproducing apparatus main drive system acting through the sheet-registering device main drive shaft 75. Shaft 75 is joumaled for rotation in thrust bearings mounted in bearing housings 76. The baring housings are locked in end caps 77 and the end caps secured in end plates 55 and 56, as for example by means of screws. As can be seen in FIG. 2, shaft 75 is supported between the end plates so that the shaft'extends external to both of said end plates. Three control cams I20, l2l,.and 122 are securely pinned at the terminus end of drive shaft 75 (FIG. 3). As shown in FIG. 2, the cams are mounted in tandem and act through their associated follower mechanisms to control the registering and forwarding functions of the instant invention. The operation of the cam control system will be explained in greater detail.

A main timing pulley 106 is also securely pinned to shaft 75 and mounted external to the adjacent end plates 55. The main timing pulley, which is driven in the direction indicated in FIG. 6 by shaft 75, acts through timing belt 80 to supply driving power to timing pulley 208 and 107.

Driving pressure rolls 97, associated with the sheet-register ing device secondary drive mechanism, are securely keyed to shaft 103 and the shaft joumaled for rotation in substantially parallel relation to the main drive shaft in bearing blocks I04 provided in the end plates. Shaft 103 is continually driven from' driving belt 80 acting through timing pulley 107. As

shown in FIG. 4, a second shaft 108 is mounted in parallelrelation to shaft 103 and has rotatably mounted thereon a pair ofupper pressure rolls 96 which are arranged to coact with driven pressure rolls 97 to support a sheet'of material in friction-driving contact therebetween. Floating bearings 109 support shaft 108 in the end plates so that the shaft is capable of being urged towards shaft 103. Sufficient biasing pressure to support a sheet in friction-driving contact between the rolls is providedby garter springs 102. The springs in grooves machines in freely rotating rollers 110 which are mounted on opposite ends of shaft 108. The spring biasing force, acting through shaft 108, urges the cooperating pressure rolls into driving contact so that a sheet of material passing therebetween is driven forward at a predetermined desired rate. It should be clear that this predetermined rate is controlled by controlling the diameter ratio between driving timing pulley 106 and driven timing pulley 107.

A second pair of pressure drive rolls are also driven from the main drive pulley timing belt 80. Drive rolls 70 are locked to shaft 61 suitably joumaled for rotation between the end plates in bearing blocks 71 so that the shaft is in parallel relation with the main drive shaft. A driving gear 84 is pinned at one end of shaft 61 and meshes with intermediate gear 81. The intermediate gear, in turn, is locked to timing pulley 208 (FIG. 6) and the entire unit rotatably mounted on stub shaft 82 staked to end plate 55. This intermediate pulley and gear arrangement serves to reverse the rotational output from timing belt so that rolls 70 move in a direction to forward a sheet passing through the registration station toward transfer station D Mounted coaxially with drive rolls 70 on drive shaft 61 are a pair of register stop rolls 60. The individual stop rolls are comprised of a pinion gear 62 which is pinned to roll member 63 by means of pin 66. The roll and pinion gear assembly are mounted on a Teflon sleeve bearing 64 adapted to freely rotate about shaft 61. As can be seen, when the register stop roll assembly is mounted on shaft 61, both the shaft and the roll assembly are capable of being driven independently. An embossed section is provided in roll member 63, the embossed section having a relatively flat stop face 67 (FIG. 4) machined thereon capable of engaging and stopping the leading edge of a sheet of support material being forwarded through the sheetregistering device. The stop face is adapted to be positioned in the path of travel of a sheet of material being forwarded between guide members 87 and 88 to intercept and retain therein a sheet of material passing through the register stop station. The stop face and guides cooperate to retain the leading edge of a sheet securely in the stop even during periods when the trailing portion of the sheet is still being moved forwardly towards the transfer station. Sufficient spacing is maintained between the lower inlet guides and the intermediate guides to pennit sheets forwarded from either tray to be buckled therebetween when the leading edge is securely held in the stop.

A pair of cooperating pressure rolls 69 are arranged to coact with the register stop rolls to support in friction driving contact therebetween a sheet of support material forwarded through the sheet-registering device. when said sheet is retained against stops 67. The pressure rolls are rotatably mounted on stub shaft 111 between pivot arms 112 by means of retainers 113. As shown in FIG. 4, the pivot arms are spring urged by spring 200 against rolls 60 and are mounted on a shaft 144 parallel to shaft 61 between the end plates in bearing blocks 115. The movement of shaft 144 in a clockwise direction, as seen in FIG. 3, will rotate the pressure rolls upwardly towards the stop rolls. Pressure rolls 68, which cooperate with driving rolls 70 are similarly retained in a rotatable manner between pivot arms 116 and the pivot arms spring urged by spring 200 against rolls 70 on shaft 143. Cams 121 and 122, which are locked to rotate with shaft 75 function to program pressure rolls 68 and 69, respectively, in and out of driving contact with the register stop rolls and with the cons' t aiitly driven rolls 70. Cam 121 imparts the desired program motion through follower arm 141 affixed to control shaft 143 to pressure rolls 69 while cam 122 similarly imparts motion through arm 140 to shaft 144 to rolls 68. Torsion springs 142, (one of which is shown in FIG. 2) are associated with the follower arm and act to bias the followers into working contact with the face of the respective cams.

The motion of the register stop rolls is controlled by means of a cam and gear arrangement as shown in FIG. 5. Control cam 120 is locked to the main drive shaft 75 and the working face of the cam communicates through L-shaped follower arm 125 with segmented gear 126. Segmented gear 126, in turn,

meshes with pinion 128 which turns shaft 129. Shaft 129 is journaled for rotation between the end plates in parallel relationship with the register stop rolls support shaft 61 so that gear 130 meshes with pinions 62 to translate the programmed motion to the register stop rolls. Cam follower arm 125 is pivoted about pin 135 and is biased into contact with the working face of the cam by means of a spring 134 acting through the segmented gear.

With the foregoing arrangement of parts in mind, the operation of the sheet-registering device of the present invention will be explained in reference to the timing diagram shown in FIG. 7. In this preferred embodiment, two xerographic images are to be processed for each revolution of the xerographic drum thus necessitating the forwarding of two sheets of final support material through registering device 22 for each revolution of the xerographic drum. It should be clear, however, this feature is not meant to be limiting in any way and is used herein for illustrative purposes. Sheet-registering device main shaft 75 is operatively connected to the xerographic apparatus main drive system so that shaft 75 turns at twice the drum speed. The drum speed is also related to image scanning and projection and to sheet feeding. Secondary feed rolls 97 and drive rolls are driven directly from main shaft through the timing belt and pulley arrangement as previously noted to drive the rolls at a predetermined constant velocity, that is, at the velocity at which the xerographic images are processed by the reproduction apparatus. The sheet feed mechanisms 50 and 51 associated with lower feed tray 34 and upper feed tray 35, respectively are also operatively connected to the xerographic apparatus drive system and arranged to forward sheets of support material in timed relation to the image processing at the predetermined machine speed.

Referring now to FIG. 7, there is shown thereon a displacement diagram relating to the movement of the leading edge of a sheet of support material as the sheet moves through sheetregistering device 22 (FIG. 1). Also graphically represented in timed relationship to the movement of the sheet are the displacement-time graphs relating to the two sets of pressure rolls and also the motion-time graph associated with the register stop rolls.

For purposes of explanation, it will be assumed that the sheet-registering device main shaft 75 is at a zero degree reference position at the instant that a sheet of support material is started forward by the upper tray feed mechanism 51 (FIG. 1). As can be seen all driving components related to the sheet-registering device of the instant invention are driven from shaft 75 and therefore the sequence of operations thereof can best be related in reference to the main shaft position. Upon machine start, that is, when the xerographic apparatus is clear of any sheets in process, sheets of support material can be fed seriatim from either the upper feed tray 35 of the lower feed tray 34 (FIG. 1) depending on the mode and sequence of operation selected. When the xerographic machine is programmed to forward sheets from the top tray, the sheet feed mechanism 51 (FIG. 1) associated therewith starts a sheet forward towards the nip between cooperating rolls 96 and 97 comprising the secondary feed transport. At this time the sheet-registering device main shaft 75 passes the zero reference position. The sheet continues to be forwarded until such time as the sheet is in friction-driving contact between the secondary feed rolls which are continually driven the upper tray feed mechanism 51 is disabled and further forstop-close position at the time that the leading edge of the first sheet reaches the registration station. That is, the stop face is in an extended position between guides 87 and 88 wherethe stop face is able to interrupt the forwarding progress of the leading edge of the first sheet.

' mediate guide members are spaced to provide sufficient room for a sheet forwarded therebetween to buckle when the leading edge of the moving sheet is arrested in the register stops.

If the machine operator selects a mode of operation which initially calls for a sheet to be forwarded from the lower feed tray, the upper feed mechanism is disabled and lower feed mechanism 50 (FIG. ll) starts a sheet forward. However, because of a path of travel from the lower sheet tray to the register stop roll is relatively shorter than that associated with the upper feed tray, the forwarding of a sheet from the lower tray does not commence until the main drive shaft has turned through approximately 210 of rotation. Sheet feed mechanism 50 transports the sheet through the lower inlet guides (FIG. 4) into the registration station where, as previously described, the leading edge of a sheet is securely retained in the now stationary register stop rolls. This occurrence also takes place as the main drive shaft rotates through 335 30'. As can be seen, the leading edge ofa sheet feed from either the upper tray or the lower tray are caused to contact the stops at the same time in reference to sheet registration sequence of operation. Atthis time, the sheet is still being forwarded under the influence of the lower tray feed mechanism to drive the leading edge of the sheet into registration and alignment with the stop rolls. The trailing portion of the sheet is allowed to buckle between the inlet guide members during this period. The sheet feed mechanism 50 is inactivated at about 340 30 of main shaft rotation.

As can be seen, the stop rolls are held in a condition to stop a sheet forwarded from'either of the sheet feed trays for approximately 9 30' of drive shaft rotation. With a sheet of support material being driven securely into the stop faces, pressure rolls 69, adapted to coact with the register stop rolls, begin to be cammed upwardly towards said register stop rolls. This occurrence takes place when the main shaft turns through a reference angle of 346. Cam 122, which is secured to the main drive shaft 75, acts through its associated follower mechanism to impart the upward motion to pressure rolls 69. As shown the registration pressure roll displacement diagram in F IG. 7, the pressure rolls 69 continue upwardly towards the register stop rolls through 360 rotation of the main drive shaft and finally reach a full up position at 4 into the next revolution.

Because of the spacial relation between the stop rolls and the pressure rolls, sufficient friction driving pressure on a sheet supported therebetween is made at about 354 of main shaft rotation and at least before the shaft has turned one full revolution. As the main shaft starts its second revolution, the registered sheet is securely locked between the stop and pressure rolls. At the start of the second revolution, cam 120, through the follower and segmented gear arrangement previously described, imparts a uniform acceleration to'the register stop rolls. This acceleration is transmitted to the sheet of support material cammed into pressure contact with the stop rolls and a sheet is rapidly and uniformly accelerated, forwarded towards the xerographic transfer station D. The programmed motion imparted to the sheet of material moves the sheet rapidly forward without slippage. The acceleration of the sheet continues through the first 50 of main drive shaft revolution at which time the desired sheet velocity is reached, that is, the sheet has attained the speed of which it is to be fed through transfer station D. Once the desired velocity is reached, the cam and gear drive continue to move the stop rolls at this velocity for the next 14 of main shaft travel. This change in motion from standstill to desired velocity is transmitted smoothly to the sheet, as reflected by the sheet displacement curve, without slippage or danger of tearing the sheet.

Pressure rolls 69 coacting with the register stop rolls, start to move out of pressure driving contact with the register stop rolls at the time that the sheet reaches constant velocity, i.e., when the main shaft has turned 50 into the second revolution. Simultaneously, cam 121 acts through its follower system to bring the pressure rolls 68 upwardly towards the constantly turning drive rolls 70 (FIG. 2). Drive rolls 70 are operatively connected to the main drive shaft through the timing belt and pulley arrangement so as to turn at the same velocity attained by the stop rolls. Thus at between 50 and 64, the coaxially mounted stop rolls and drive rolls are moving at synchronous speeds although driven independently through different mechanisms. Between 55 30 and 58 30' both sets of register stop rolls and driving rolls are in friction-driving contact with a single sheet of support material being forwarded through the sheet-registering device. The respective sets of pressure rolls continue to be cycled by the associated cam systems until the sheet forwarding function is shifted entirely from the stop rolls 60 to the drive rolls 70. The transition from one set of driving members to the other is made in positive manner precluding the possibility of the registered sheets from slipping or being skewed out of alignment as they are fed forward into the xerographic transfer station. It should be noted that the motion of the sheet as it moves through the registration station is positively and continuously controlled. Furthermore, because the motion of the sheet is positively controlled the sheet movement is capable of being accurately related to the movement of a xerographic image on the drum surface thus insuring accurate transferring of the image to the sheet of final support material.

Although not necessary it is preferred to fabricate drive rolls 70 to a slightly smaller diameter than the diameter of the register stop rolls. Sufficient clearance is allowed so a sheet cammed into pressure contact with the register stop rolls will not be in contact with the driving rolls. However, this clearance should not be so great that pressure contact will not be maintained between driving rolls 70 and pressure rolls 68 when the latter are subsequently cammed into an operative position.

The sheet continues to move forward under the influence of rolls 70 and pressure rolls 6% until the main drive shaft has turned 228 at which time the pressure rolls begin to be cammed away from the driving rolls. Friction driving contact is lost at approximately 238 and the pressure rolls 68 reach a full'down position at 246. At this time the trailing edge of the sheet has cleared the register station. During the period when the sheet-forwarding function is being carried out by driving rolls 70, the register stop rolls are decelerated to a stop (123) and after a short dwell time (4) start to swing back towards the original stop closedposition. At 268 of main shaft rotation, at which time the first sheet in process has cleared the registration station, the flat stop face 67 is moved in behind the trailing edge of the sheet into a position where the face is able to intercept the next subsequent sheet being forwarded. It should be noted at this point that during the second revolution of the main drive shaft the next sheet to be processed has started through the appropriate guide and the leading edge of the sheet is in a position to contact the closed stops at 335 30' of the second revolution.

While the invention has been described with reference to the structure disclosed herein, it is not confined to the details set forth, and this application is intended to cover such modifications or changes as may come within the purposes of the improvements of the scope of the following claims.

1. Apparatus to register and forward cut sheets of material fed from a sheet supply station along a predetermined path of travel including a plurality of register rolls mounted on a supporting shaft for rotation independently thereof said rolls being coaxially aligned adjacent to said path of travel, each of said rolls having a stop surface thereon being capable-of extending into said path of travel to engage the leading edge of a sheet forwarded therealong whereby said sheet is registered against said stop surfaces to support the sheet in pressure contact against said register rolls,

a first camming means to move a first set of pinch rolls into engagement with a sheet registered against the stops and hold said pinch rolls in engagement therewith for a predetermined period of time,

control means to rotate said register rolls during the period of pinch roll engagement to accelerate a sheet held in contact therewith to a predetermined constant velocity and maintain said sheet at said constant velocity,

a plurality of drive rolls coaxially aligned with said register rolls on said supporting shaft, the drive rolls having an outer surface thereon being continually moving at said predetermined constant velocity,

:1 second set of pinch rolls arranged to move into contact with a sheet engaged by said register rolls to hold said sheet in pressure contact against said constantly rotated drive rolls, and

second camming means to move said second set of pinch rolls into engagement with a sheet moving at the constant velocity.

2. The apparatus of claim 1, wherein the camming means to move said first and second pinch rolls comprise a cam and a follower arm which are moving in timed relation with said control means.

3. The apparatus of claim 2, wherein said second set of pinch rolls are moved into engagement with the moving sheet during the predetermined period in which said first set of pinch rolls are in engagement with said sheet.

4. The apparatus of claim 3, further including subsequent sheet-advancing means arranged to engage a sheet moving at the constant velocity and forward said sheet to a subsequent processing station.

5. The apparatus of claim 4, wherein said control means returns said register rolls to a position wherein the stop surfaces thereon are in a condition to engage the next subsequent sheet forwarded from the supply station after the trailing edge of the sheet has cleared said register rolls.

6. in a copying apparatus of the type wherein individual cut sheets of support material are forwarded one at a time through a sheet-registering station, the apparatus including a shaftjournaled for rotation in the sheet-registering station,

a pair of register rolls mounted to rotate freely upon said shaft, each of said rolls having a stop surface thereon positionable to engage the leading edge of a sheet forwarded through the sheet-registering station whereby the leading edge of the sheet is registered against said stop surfaces,

a pair of drive rolls secured to said shaft being coaxially aligned with said register rolls and being arranged to rotate with said shaft,

drive means to rotate said shaft at a rate wherein the outer surface of said drive rolls moves at a constant velocity,

means to hold a sheet registered stop surfaces in pressure contact against the surface of said register rolls for a predetermined period of time,

control means to rotate said register rolls in a direction wherein the stop surfaces are moved out of sheet engagement and a sheet registered against the stops is accelerated to said constant velocity during the period in which the sheet is held in pressure contact against said register rolls, and

means to place the sheet moving at said constant velocity into pressure contact with the drive rolls wherein the sheet is forwarded from said sheet-registering station at said constant velocity. 7. The apparatus of claim 6, wherein said control means associated with the register rolls is arranged to accelerate and forward a sheet in engagement therewith in less than one complete revolution ofsaid register rolls.

8. The apparatus of claim 7, further including guide means arranged to direct sheets forwarded from a plurality of sheets supply stacks into engagement with said stop faces on said register rolls. 

1. Apparatus to register and forward cut sheets of material fed from a sheet supply station along a predetermined path of travel including a plurality of register rolls mounted on a supporting shaft for rotation independently thereof said rolls being coaxially aligned adjacent to said path of travel, each of said rolls having a stop surface thereon being capable of extending into said path of travel to engage the leading edge of a sheet forwarded therealong whereby said sheet is registered against said stop surfaces to support the sheet in pressure contact against said register rolls, a first camming means to move a first set of pinch rolls into engagement with a sheet registered against the stops and hold said pinch rolls in engagement therewith for a predetermined period of time, control means to rotate said register rolls during the period of pinch roll engagement to accelerate a sheet held in contact therewith to a predetermined constant velocity and maintain said sheet at said constant velocity, a plurality of drive rolls coaxially aligned with said register rolls on said supporting shaft, the drive rolls having an outer surface thereon being continually moving at said predetermined constant velocity, a second set of pinch rolls arranged to move into contact with a sheet engaged by said register rolls to hold said sheet in pressure contact against said constantly rotated drive rolls, and second camming means to move said second set of pinch rolls into engagement with a sheet moving at the constant velocity.
 2. The apparatus of claim 1, wherein the camming means to move said first and second pinch rolls comprise a cam and a follower arm which are moving in timed relation with said control means.
 3. The apparatus of claim 2, wherein said second set of pinch rolls are moved into engagement with the moving sheet during the predetermined period in which said first set of pinch rolls are in engagement with said sheet.
 4. The apparatus of claim 3, further including subsequent sheet-advancing means arranged to engage a sheet moving at the constant velocity and forward said sheet to a subsequent processing station.
 5. The apparatus of claim 4, wherein said control means returns said register rolls to a position wherein the stop surfaces thereon are in a condition to engage the next subsequent sheet forwarded from the supply station after the trailing edge of the sheet has cleared said register rolls.
 6. In a copying apparatus of the type wherein individual cut sheets of support material are forwarded one at a time through a sheet-registering station, the apparatus including a shaft journaled for rotation in the sheet-registering station, a pair of register rolls mounted to rotate freely upon said shaft, each of said rolls having a stop surface thereon positionable to engage the leading edge of a sheet forwarded through the sheet-registering station whereby the leading edge of the sheet is registered against said stop surfaces, a pair of drive rolls secured to said shaft being coaxially aligned with said register rolls and being arranged to rotate with said shaft, drive means to rotate said shaft at a rate wherein the outer surface of said drive rolls moves at a constant velocity, means to hold a sheet registered stop surfaces in pressure contact against the surface of said register rolls for a predetermined period of time, control means to rotate said register rolls in a direction wherein the stop surfaces are moved out of sheet engagement and a sheet registered against the stops is accelerated to said constant velocity during the period in which the sheet is held In pressure contact against said register rolls, and means to place the sheet moving at said constant velocity into pressure contact with the drive rolls wherein the sheet is forwarded from said sheet-registering station at said constant velocity.
 7. The apparatus of claim 6, wherein said control means associated with the register rolls is arranged to accelerate and forward a sheet in engagement therewith in less than one complete revolution of said register rolls.
 8. The apparatus of claim 7, further including guide means arranged to direct sheets forwarded from a plurality of sheets supply stacks into engagement with said stop faces on said register rolls. 